Lithium battery has been widely used in portable electronic products. Along with the development of electric vehicles, the need of relevant materials has attracted people's attention. Lithium battery has the advantage of high energy density, and complies with the requirement of power lithium battery for electric vehicles. However, due to the large power output and size increase of the battery, a large volume of heat will be generated during the operation. Without an effective protection mechanism, thermal runaway may easily occur and cause the battery to burn and explore. Thus, the separator is very crucial to the safety of lithium battery. The separator is disposed between two electrodes for conducting the ions to trigger electrochemical reaction. Thus, the separator needs to have excellent ion conductivity and possess sufficient mechanic strength and penetration resistance to avoid the lithium dendrite during electrochemical reaction penetrating the separator and causing short-circuiting. When temperature arises abnormally, the thermal closed-pore feature of the separator will block ion conduction and terminate electrochemical reaction to avoid the heat being released continuously.